Before the test, my assumption was that smaller files would mean more files dumped to the memory card before it stuttered, and that small jpegs should allow a much larger number than full sized RAW files. In fact, the opposite happened.

I interpet the results to mean that my assumption of writting the files to the flash drive being the bottleneck was wrong. It seems obvious that the internal memory becomes filled with RAW data waiting to be converted to Jpeg... the bottleneck is processing to Jpeg.... get rid of that process and the number of pictures before stuttering doubles. The next bottleneck is processing the raw files (including reading them off of the sensor), changing the output RAW size has almost no effect on the buffer, so once again, the flash card is not the bottleneck.

So the limitation is computing power.... not card speed. Anyone care to try this test on a different camera model?

Before the test, my assumption was that smaller files would mean more files dumped to the memory card before it stuttered, and that small jpegs should allow a much larger number than full sized RAW files. In fact, the opposite happened.

I interpet the results to mean that my assumption of writting the files to the flash drive being the bottleneck was wrong. It seems obvious that the internal memory becomes filled with RAW data waiting to be converted to Jpeg... the bottleneck is processing to Jpeg.... get rid of that process and the number of pictures before stuttering doubles. The next bottleneck is processing the raw files (including reading them off of the sensor), changing the output RAW size has almost no effect on the buffer, so once again, the flash card is not the bottleneck.

So the limitation is computing power.... not card speed. Anyone care to try this test on a different camera model?

7d, 8fps, ISO 100, 1/1000, nifty-fifty @ f/1.8:

RAW 28framesJPEG (L): Until I didn't want to have to delete any more. Which was 100 frames. and it was done writing as soon as I was done (no lingering red light for "card busy")

Out of curiosity, what card did you use? Maybe that does matter... mine's a SanDisk Extreme (60 MB/s) 16GB...

Don, what card were you using? I did a similar test with my 60D and took well over 100 frames in JPG (large) without filling the buffer. Same results with a 7D and 5D2/3 (all CF, no SD used on the 5D3).

Regarding RAW, when I went from a Patriot Class 6 SD card to a SanDisk Extreme I saw a major jump in how quickly it recovered from a RAW burst (flushed the buffer to the card). I don't remember exact times, but it was a significant change - probably 12 seconds before the red light went off vs 20.

The High ISO Noise Reduction (which is actually active at all ISO settings) on the Canon cameras will drop the camera's ability to buffer photos drastically. I shoot some basketball games in some poorly lit high school gyms and rather than limit myself to single shots with a flash I pump up the ISO to 4000 or 5000 most nights. I shoot with Noise Reduction set to high and I can only shoot four photos in a burst with my 7d.

The High ISO Noise Reduction (which is actually active at all ISO settings) on the Canon cameras will drop the camera's ability to buffer photos drastically. I shoot some basketball games in some poorly lit high school gyms and rather than limit myself to single shots with a flash I pump up the ISO to 4000 or 5000 most nights. I shoot with Noise Reduction set to high and I can only shoot four photos in a burst with my 7d.

I thought in-camera noise reduction while shooting in RAW didn't do anything...?

The High ISO Noise Reduction (which is actually active at all ISO settings) on the Canon cameras will drop the camera's ability to buffer photos drastically. I shoot some basketball games in some poorly lit high school gyms and rather than limit myself to single shots with a flash I pump up the ISO to 4000 or 5000 most nights. I shoot with Noise Reduction set to high and I can only shoot four photos in a burst with my 7d.

I thought in-camera noise reduction while shooting in RAW didn't do anything...?

The High ISO Noise Reduction (which is actually active at all ISO settings) on the Canon cameras will drop the camera's ability to buffer photos drastically. I shoot some basketball games in some poorly lit high school gyms and rather than limit myself to single shots with a flash I pump up the ISO to 4000 or 5000 most nights. I shoot with Noise Reduction set to high and I can only shoot four photos in a burst with my 7d.

You were bang on. I set High ISO Noise Reduction to disabled and was unable to fill the buffer shooting continuously.... I gave up after 150 shots.

My earlier observations showed that it had to be a computing power problem. If it was a card wrtite speed problem changing the raw file settings would have sped up the rate, but it had no effect... Likewise, if it was a write speed problem, why would 8 tiny jpegs fill the buffer quicker than 16 large raws?

Thanks for the tip.... I had assumed that high ISO reduction would only affect high ISO shots, not everything.... and I was wrong.